But update methord is not like that. It will call every 300 ms as a never ending 'for loop'. From that metord call, it will detect whether user press any key. Also it id used for write logic of the game.

So  you need to be careful think when you writing codes in that methord.

protected override void Draw(GameTime gameTime)

        {

            GraphicsDevice.Clear(Color.CornflowerBlue);

             // TODO: Add your drawing code here

             base.Draw(gameTime);

        }

This method is similar as the update method. It also calls in every 300 ms. And this method is using for draw 2d and 3d graphics.

You can do all the 2d and 3d rendering of the game in this method call.

Now I think you know the basic method calls and class structure of a XNA game.

All these codes are automatically generated when you load a windows game project.

Default Game1.cs file

using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Audio;

using Microsoft.Xna.Framework.Content;

using Microsoft.Xna.Framework.GamerServices;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

using Microsoft.Xna.Framework.Media;

using Microsoft.Xna.Framework.Net;

using Microsoft.Xna.Framework.Storage;

namespace WindowsGame1

{

    /// <summary>

    /// This is the main type for your game

    /// </summary>

    public class Game1 : Microsoft.Xna.Framework.Game

    {

        GraphicsDeviceManager graphics;

        SpriteBatch spriteBatch;

        SpriteFont myfont;

        public Game1()

        {

            graphics = new GraphicsDeviceManager(this);

            Content.RootDirectory = "Content";

        }

        /// <summary>

        /// Allows the game to perform any initialization it needs to before starting to run.

        /// This is where it can query for any required services and load any non-graphic

        /// related content.  Calling base.Initialize will enumerate through any components

        /// and initialize them as well.

        /// </summary>

        protected override void Initialize()

        {

            // TODO: Add your initialization logic here

            base.Initialize();

        }

        /// <summary>

        /// LoadContent will be called once per game and is the place to load

        /// all of your content.

        /// </summary>

        protected override void LoadContent()

        {

            // Create a new SpriteBatch, which can be used to draw textures.

            spriteBatch = new SpriteBatch(GraphicsDevice);

            myfont = Content.Load<SpriteFont>("Arial");

            // TODO: use this.Content to load your game content here

        }

        /// <summary>

        /// UnloadContent will be called once per game and is the place to unload

        /// all content.

        /// </summary>

        protected override void UnloadContent()

        {

            // TODO: Unload any non ContentManager content here

        }

        /// <summary>

        /// Allows the game to run logic such as updating the world,

        /// checking for collisions, gathering input, and playing audio.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Update(GameTime gameTime)

        {

            // Allows the game to exit

            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)

                this.Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);

        }

        /// <summary>

        /// This is called when the game should draw itself.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Draw(GameTime gameTime)

        {

            GraphicsDevice.Clear(Color.CornflowerBlue);

            // TODO: Add your drawing code here

            base.Draw(gameTime);

        }

    }

}

To write a hello world game, first you need to load font to the content folder.

Right click on the content folder and Add->new item

And select Sprite font and rename that as  Arial.spritefont

Arial is the name of the font we are going to use.

You can use any font that install in the Windows font folder.

Go to Arial.spritefont file

if you like you can change the size and style by modifing Size and Style tags.

<Size>14</Size>

<Style>Regular</Style>

Final   Arial.spritefont  file.

<?xml version="1.0" encoding="utf-8"?>

<!--

This file contains an xml description of a font, and will be read by the XNA

Framework Content Pipeline. Follow the comments to customize the appearance

of the font in your game, and to change the characters which are available to draw

with.

-->

<XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics">

  <Asset Type="Graphics:FontDescription">

    <!--

    Modify this string to change the font that will be imported.

    -->

    <FontName>Kootenay</FontName>

    <!--

    Size is a float value, measured in points. Modify this value to change

    the size of the font.

    -->

    <Size>14</Size>

    <!--

    Spacing is a float value, measured in pixels. Modify this value to change

    the amount of spacing in between characters.

    -->

    <Spacing>0</Spacing>

    <!--

    UseKerning controls the layout of the font. If this value is true, kerning information

    will be used when placing characters.

    -->

    <UseKerning>true</UseKerning>

    <!--

    Style controls the style of the font. Valid entries are "Regular", "Bold", "Italic",

    and "Bold, Italic", and are case sensitive.

    -->

    <Style>Regular</Style>

    <!--

    If you uncomment this line, the default character will be substituted if you draw

    or measure text that contains characters which were not included in the font.

    -->

    <!-- <DefaultCharacter>*</DefaultCharacter> -->

    <!--

    CharacterRegions control what letters are available in the font. Every

    character from Start to End will be built and made available for drawing. The

    default range is from 32, (ASCII space), to 126, ('~'), covering the basic Latin

    character set. The characters are ordered according to the Unicode standard.

    See the documentation for more information.

    -->

    <CharacterRegions>

      <CharacterRegion>

        <Start> </Start>

        <End>~</End>

      </CharacterRegion>

    </CharacterRegions>

  </Asset>

</XnaContent>

Now in the Game 1.cs you need to write code to draw a string in the screan. Still we didn`t write any code in our game. Only did the renaming of fonts.

First create a object form SpriteFont to handle our font.

SpriteFont myfont;

Then in the LoadContent()  metord you can load the font.

myfont = Content.Load<SpriteFont>("Arial");

then in the Draw()metord you can draw the font in the sceran.

spriteBatch.Begin();   / /start the sprite batch process to draw font

//drawString() mathord is getting parameters for font type,string valuve,x and y positions in the screan where you need to put the string,and the font color.

                     //draw the font in the screan

spriteBatch.End();   //end the sprite batch process

now you can run the project by pressing F5 or by clicking the run button.

 Final code of Game1.cs

using System.Collections.Generic;

using System.Linq;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Audio;

using Microsoft.Xna.Framework.Content;

using Microsoft.Xna.Framework.GamerServices;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

using Microsoft.Xna.Framework.Media;

using Microsoft.Xna.Framework.Net;

using Microsoft.Xna.Framework.Storage;

namespace WindowsGame1

{

    /// <summary>

    /// This is the main type for your game

    /// </summary>

    public class Game1 : Microsoft.Xna.Framework.Game

    {

        GraphicsDeviceManager graphics;

        SpriteBatch spriteBatch;

        SpriteFont myfont;

        public Game1()

        {

            graphics = new GraphicsDeviceManager(this);

            Content.RootDirectory = "Content";

        }

        /// <summary>

        /// Allows the game to perform any initialization it needs to before starting to run.

        /// This is where it can query for any required services and load any non-graphic

        /// related content.  Calling base.Initialize will enumerate through any components

        /// and initialize them as well.

        /// </summary>

        protected override void Initialize()

        {

            // TODO: Add your initialization logic here

            base.Initialize();

        }

        /// <summary>

        /// LoadContent will be called once per game and is the place to load

        /// all of your content.

        /// </summary>

        protected override void LoadContent()

        {

            // Create a new SpriteBatch, which can be used to draw textures.

            spriteBatch = new SpriteBatch(GraphicsDevice);

            myfont = Content.Load<SpriteFont>("Arial");

            // TODO: use this.Content to load your game content here

        }

        /// <summary>

        /// UnloadContent will be called once per game and is the place to unload

        /// all content.

        /// </summary>

        protected override void UnloadContent()

        {

            // TODO: Unload any non ContentManager content here

        }

        /// <summary>

        /// Allows the game to run logic such as updating the world,

        /// checking for collisions, gathering input, and playing audio.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Update(GameTime gameTime)

        {

            // Allows the game to exit

            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)

                this.Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);

        }

        /// <summary>

        /// This is called when the game should draw itself.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Draw(GameTime gameTime)

        {

            GraphicsDevice.Clear(Color.CornflowerBlue);

            spriteBatch.Begin();

            spriteBatch.DrawString(myfont, "Hello world", new Vector2(10.0f, 10.0f), Color.Black);

            spriteBatch.End();

            base.Draw(gameTime);

        }

    }}

This is the end of the First hello world program.

For this application it only took 5 lines of code.

If you are using unmanged c++ code to hello world programe it takes about 200 lines of code.

So its lot easier to develop XNA games using C#.

From next tutorial you learn about working with 2d graphics in XNA.

Uditha Sampath Bandara.

Lead game developer.

http://uditha.wordpress.com/